There are a lot of preschools in Elmhurst!
I highly recommend Timothy Christian. The preschool room is beautiful, the classes are mixed age, which I believe is a tremendous benefit, and they actually follow a written curriculum. Additionally, the teachers are lovely.
There are two Montessori preschools in town and, of the two, I'd recommend Wilson Montessori.
I'd steer clear of both Tree Town, which is a cooperative preschool, and Bethel Learning Center, which in my opinion is an awful place.
If you're looking for a full-time preschool that is more on the daycare spectrum, Elmhurst Academy is well-respected -- and very expensive.
There are also three Catholic churches in town and each has a preschool. Many people who intend to send their child to either Immaculate Conception or Visitation for grade school enroll them in the preschool.
There are several other churches in town that also have preschools but I've never visited any of them.
I guess it's good to have options! Oh, one other thing, preschool registration for the following year is in January and many of the schools fill up quickly. If you're looking for some place now I know that most of the schools have waiting lists for spaces that open up.